As the size of semiconductor devices has continued to shrink and circuit densities have increased accordingly, thermal management of these devices has become more challenging. In the past, thermal management in semiconductor devices was often addressed through the use of forced convective air cooling, either alone or in conjunction with various heat sink devices, and was accomplished through the use of fans. However, fan-based cooling systems are undesirable due to the electromagnetic interference and noise attendant to their use. Moreover, the use of fans also requires relatively large moving parts, and corresponding high power inputs, in order to achieve the desired level of heat transfer. Furthermore, while fans are adequate for providing global movement of air over electronic devices, they generally provide insufficient localized cooling to provide adequate heat dissipation for the hot spots that typically exist in a semiconductor device.
More recently, thermal management systems have been developed which utilize synthetic jet ejectors. These systems are more energy efficient than comparable fan-based systems, and also offer reduced levels of noise and electromagnetic interference. Systems of this type are described in greater detail in U.S. Pat. No. 6,588,497 (Glezer et al.). The use of synthetic jet ejectors has proven very efficient in providing localized heat dissipation, and hence can be used to address hot spots in semiconductor devices. Synthetic jet ejectors may be used in conjunction with fan-based systems to provide thermal management systems that afford both global and localized heat dissipation.
One example of a thermal management system that utilizes synthetic jet ejectors is illustrated in FIG. 1. The system shown therein utilizes an air-cooled heat transfer module 101 which is based on a ducted heat ejector (DHE) concept. The module utilizes a thermally conductive, high aspect ratio duct 103 that is thermally coupled to one or more IC packages 105. Heat is removed from the IC packages 105 by thermal conduction into the duct shell 107, where it is subsequently transferred to the air moving through the duct. The air flow within the duct 103 is induced through internal forced convection by a pair of low form factor synthetic jet ejectors 109 which are integrated into the duct shell 107. In addition to inducing air flow, the turbulent jet produced by the synthetic jet ejector 109 enables highly efficient convective heat transfer and heat transport at low volume flow rates through small scale motions near the heated surfaces, while also inducing vigorous mixing of the core flow within the duct.
Thermal management systems are also known which are based on heat pipes. Heat pipes are devices that can quickly transfer heat from one point to another with almost no heat loss. A typical heat pipe consists of a sealed aluminum or copper container whose inner surfaces have a capillary wicking material disposed thereon. Heat pipes have the ability to transport heat against gravity by an evaporation-condensation cycle with the help of porous capillaries that form the wicking material. The wick provides the capillary driving force which returns the condensate to the evaporator.
FIG. 2 shows a specific example of one known heat pipe. As shown therein, the device 151 includes a coolant storing part 153 for storing a liquid coolant, and a heat absorbing part 155 that is adapted to absorb heat from a heat source and that includes at least one micro channel 157. The heat absorbing part 155 is positioned close to the heat source and is in liquid communication with the coolant storing part 153. The liquid coolant is partly filled in the micro-channel 157 by surface tension where it is vaporized to become a gaseous coolant when heat is absorbed from the heat generating source. The device 151 includes a heat insulating part 159 positioned adjacent to the heat absorbing part 155 to prevent the heat absorbed by the heat absorbing part 155 from transferring to other zones. The device 151 also includes a condensing part 161, positioned apart from the heat absorbing part, for condensing the gaseous coolant. The device 151 is also equipped with a gas moving part 163 positioned near the heat absorbing part 155 and the condensing part 161. The gas moving part 163 includes a passage through which the gaseous coolant moves from the heat absorbing part 155 to the condensing part 161. The device 151 further includes a housing 165 in which at least the heat absorbing part is housed.
While the above noted systems represent notable improvements in the art, the need still exists for thermal management systems that have improved heat transfer efficiencies. This need, and other needs, are met by the devices and methodologies disclosed herein.